Simulation of the fuel-assembly bowing in PWR based on the coupling of pin-resolved neutronics and pin-by-pin subchannel

In recent years, some nuclear power reactors have experienced power tilts. According to the technical specifications for the operation of the nuclear power plant (NPP), the reactor can only be operated at a power level below 100%, which seriously affects the economic efficiency of NPPs. The bowing of fuel assemblies, which can lead to a power tilt, is investigated in this study, and the simulation method that considers fuel-assembly bowing in high-fidelity neutronics and thermohydraulic coupling is conducted. For the neutronics calculations, the equivalent density method is proposed to simulate the fuel-assembly bowing. The effect of the fuel-assembly bowing on the thermohydraulic feedback was taken into account by changing the flow area of the cooling channels. Some tests were performed to verify the results of the proposed method. The results show that the proposed simulation method can be used to study and analyze the power tilts caused by the fuel-assembly bowing in advanced PWRs.